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<HTML>
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<TITLE>filter1d</TITLE>
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<BODY>
<H1>filter1d</H1>
<HR>
<PRE>
<!-- Manpage converted by man2html 3.0.1 -->
filter1d - Time domain filtering of 1-D time series
</PRE>
<H2>SYNOPSIS</H2><PRE>
<B>filter1d</B> [ <I>infile</I> ] <B>-F</B><I><type><width></I> [ <B>-D</B><I>increment</I> ] [ <B>-E</B> ]
[ <B>-H</B>[<I>nrec</I>] ] [ <B>-I</B><I>ignore</I><B>_</B><I>val</I> ] [ <B>-L</B><I>lack</I><B>_</B><I>width</I> ] [
<B>-N</B><I>n</I><B>_</B><I>cols/t</I><B>_</B><I>col</I> ] [ <B>-Q</B><I>q</I><B>_</B><I>factor</I> ] [ <B>-S</B><I>symmetry</I><B>_</B><I>factor</I> ] [
<B>-T</B><I>start/stop/int</I> ] [ <B>-V</B> ] [ <B>-bi</B>[<B>s</B>][<I>n</I>] ] [ <B>-bo</B>[<B>s</B>] ]
</PRE>
<H2>DESCRIPTION</H2><PRE>
<B>filter1d</B> is a general time domain filter for multiple col
umn time series data. The user specifies the number of
columns of input and which column is the time. (See <B>-N</B>
option below). The fastest operation occurs when the input
time series are equally spaced and have no gaps or out
liers and the special options are not needed. <B>filter1d</B>
has options L, Q, and S for unevenly sampled data with
gaps.
<I>infile</I> Multi-column ASCII (or binary, see <B>-b</B>) file holding
data values to be filtered.
<B>-F</B> sets Filtertype, <I>type</I> is one of <B>b</B>(oxcar), <B>c</B>(osine
arch), <B>g</B>(aussian), <B>m</B>(edian), or <B>p</B>(maximum likeli
hood Probability estimator -- a mode estimator),
and specify full filter <I>width</I> in same units as time
column, OR, use <B>-Ff</B><I>name</I> to give the name of a one-
column file of your own coefficients. Upper case
type <B>B,</B> <B>C,</B> <B>G,</B> <B>M,</B> <B>P,</B> <B>F</B> will use robust filter ver
sions: i.e., replace outliers (2.5 L1 scale off
median) with median during filtering.
</PRE>
<H2>OPTIONS</H2><PRE>
<B>-D</B> <I>increment</I> is used when series is NOT equidistantly
sampled. Then <I>increment</I> will be the abscissae res
olution, i.e., all abscissae will be rounded off to
a multiple of <I>increment</I>. Alternatively, resample
data with <B><A HREF="sample1d.html">sample1d</A></B>.
<B>-E</B> Include Ends of time series in output. Default
loses half the filter-width of data at each end.
<B>-H</B> Input file(s) has Header record(s). Number of
header records can be changed by editing your .gmt
defaults file. If used, <B><A HREF="GMT.html">GMT</A></B> default is 1 header
record.
<B>-I</B> To ignore values; If an input value equals
<I>ignore</I><B>_</B><I>val</I> it will be set to NaN.
<B>-L</B> Checks for Lack of data condition. If input data
has a gap exceeding <I>width</I> then no output will be
given at that point [Default does not check Lack].
contains the independent variable (time). The left-
most column is # 0, the right-most is # (<I>n</I><B>_</B><I>cols</I> -
1). [Default is <I>n</I><B>_</B><I>cols</I> = 2, <I>t</I><B>_</B><I>col</I> = 0; i.e., file
has t, f(t) pairs].
<B>-Q</B> assess Quality of output value by checking mean
weight in convolution. Enter <I>q</I><B>_</B><I>factor</I> between 0
and 1. If mean weight < <I>q</I><B>_</B><I>factor</I>, output is sup
pressed at this point [Default does not check Qual
ity].
<B>-S</B> Checks symmetry of data about window center. Enter
a factor between 0 and 1. If ( (abs(n_left -
n_right)) / (n_left + n_right) ) > <I>factor</I>, then no
output will be given at this point [Default does
not check Symmetry].
<B>-T</B> Make evenly spaced timesteps from <I>start</I> to <I>stop</I> by
<I>int</I> [Default uses input times].
<B>-V</B> Selects verbose mode, which will send progress
reports to stderr [Default runs "silently"].
<B>-bi</B> Selects binary input. Append <B>s</B> for single precision
[Default is double]. Append <I>n</I> for the number of
columns in the binary file(s).
<B>-bo</B> Selects binary output. Append <B>s</B> for single preci
sion [Default is double].
</PRE>
<H2>EXAMPLES</H2><PRE>
To filter the data set in the file cruise.gmtd containing
evenly spaced gravity, magnetics, topography, and distance
(in m) with a 10 km Gaussian filter, removing outliers,
and output a filtered value every 2 km between 0 and 100
km, try
filter1d cruise.gmtd <B>-T</B>0/1.0e5/2000 <B>-FG</B>10000 <B>-N</B>4/3 <B>-V</B> >
filtered_cruise.gmtd
Data along track often have uneven sampling and gaps which
we do not want to interpolate using <B><A HREF="sample1d.html">sample1d</A></B>. To find the
median depth in a 50 km window every 25 km along the track
of cruise v3312, stored in v3312.dt, checking for gaps of
10km and asymmetry of 0.3, try
filter1d v3312.dt <B>-FM</B>50 <B>-T</B>0/100000/25 <B>-L</B>10 <B>-S</B>0.3 >
v3312_filt.dt
</PRE>
<H2>SEE ALSO</H2><PRE>
<I>gmt</I>(l), <I><A HREF="sample1d.html">sample1d</A></I>(l)
</PRE>
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